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Message-Id: <20220121001204.4023842-1-keescook@chromium.org>
Date: Thu, 20 Jan 2022 16:12:04 -0800
From: Kees Cook <keescook@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
Masahiro Yamada <masahiroy@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Nathan Chancellor <nathan@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Helge Deller <deller@....de>,
Daniel Latypov <dlatypov@...gle.com>,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v2] Kconfig.debug: Make DEBUG_INFO selectable from a choice
Currently it's not possible to enable DEBUG_INFO for an all*config build,
since it is marked as "depends on !COMPILE_TEST". This generally makes
sense because a debug build of an all*config target ends up taking much
longer and the output is much larger. Having this be "default off" makes
sense. However, there are cases where enabling DEBUG_INFO for such builds
is useful for doing treewide A/B comparisons of build options, etc.
Make DEBUG_INFO selectable from any of the DWARF version choice options,
with DEBUG_INFO_NONE being the default for COMPILE_TEST. The mutually
exclusive relationship between DWARF5 and BTF must be inverted, but the
result remains the same. Additionally moves DEBUG_KERNEL and DEBUG_MISC
up to the top of the menu because they were enabling features _above_
it, making it weird to navigate menuconfig.
Suggested-by: Arnd Bergmann <arnd@...db.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Masahiro Yamada <masahiroy@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
v1: https://lore.kernel.org/lkml/20211210000910.3597609-1-keescook@chromium.org/
v2:
- simplify default vs COMPILE_TEST (Arnd, Masahiro)
- add Reviewed/Tested-by tags
---
lib/Kconfig.debug | 141 ++++++++++++++++++++++++----------------------
1 file changed, 75 insertions(+), 66 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5c12bde10996..3be525ad0013 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -208,20 +208,88 @@ config DEBUG_BUGVERBOSE
endmenu # "printk and dmesg options"
+config DEBUG_KERNEL
+ bool "Kernel debugging"
+ help
+ Say Y here if you are developing drivers or trying to debug and
+ identify kernel problems.
+
+config DEBUG_MISC
+ bool "Miscellaneous debug code"
+ default DEBUG_KERNEL
+ depends on DEBUG_KERNEL
+ help
+ Say Y here if you need to enable miscellaneous debug code that should
+ be under a more specific debug option but isn't.
+
menu "Compile-time checks and compiler options"
config DEBUG_INFO
- bool "Compile the kernel with debug info"
- depends on DEBUG_KERNEL && !COMPILE_TEST
+ bool
help
- If you say Y here the resulting kernel image will include
- debugging info resulting in a larger kernel image.
+ A kernel debug info option other than "None" has been selected
+ in the "Debug information" choice below, indicating that debug
+ information will be generated for build targets.
+
+choice
+ prompt "Debug information"
+ depends on DEBUG_KERNEL
+ default DEBUG_INFO_NONE if COMPILE_TEST
+ help
+ Selecting something other than "None" results in a kernel image
+ that will include debugging info resulting in a larger kernel image.
This adds debug symbols to the kernel and modules (gcc -g), and
is needed if you intend to use kernel crashdump or binary object
tools like crash, kgdb, LKCD, gdb, etc on the kernel.
- Say Y here only if you plan to debug the kernel.
- If unsure, say N.
+ Choose which version of DWARF debug info to emit. If unsure,
+ select "Toolchain default".
+
+config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
+ bool "Rely on the toolchain's implicit default DWARF version"
+ select DEBUG_INFO
+ help
+ The implicit default version of DWARF debug info produced by a
+ toolchain changes over time.
+
+ This can break consumers of the debug info that haven't upgraded to
+ support newer revisions, and prevent testing newer versions, but
+ those should be less common scenarios.
+
+config DEBUG_INFO_DWARF4
+ bool "Generate DWARF Version 4 debuginfo"
+ select DEBUG_INFO
+ help
+ Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
+
+ If you have consumers of DWARF debug info that are not ready for
+ newer revisions of DWARF, you may wish to choose this or have your
+ config select this.
+
+config DEBUG_INFO_DWARF5
+ bool "Generate DWARF Version 5 debuginfo"
+ select DEBUG_INFO
+ depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
+ help
+ Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
+ 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
+ draft features until 7.0), and gdb 8.0+.
+
+ Changes to the structure of debug info in Version 5 allow for around
+ 15-18% savings in resulting image and debug info section sizes as
+ compared to DWARF Version 4. DWARF Version 5 standardizes previous
+ extensions such as accelerators for symbol indexing and the format
+ for fission (.dwo/.dwp) files. Users may not want to select this
+ config if they rely on tooling that has not yet been updated to
+ support DWARF Version 5.
+
+config DEBUG_INFO_NONE
+ bool "Disable debug information"
+ help
+ Do not build the kernel with debugging information, which will
+ result in a faster and smaller build.
+
+endchoice # "Debug information"
if DEBUG_INFO
@@ -267,55 +335,11 @@ config DEBUG_INFO_SPLIT
to know about the .dwo files and include them.
Incompatible with older versions of ccache.
-choice
- prompt "DWARF version"
- help
- Which version of DWARF debug info to emit.
-
-config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
- bool "Rely on the toolchain's implicit default DWARF version"
- help
- The implicit default version of DWARF debug info produced by a
- toolchain changes over time.
-
- This can break consumers of the debug info that haven't upgraded to
- support newer revisions, and prevent testing newer versions, but
- those should be less common scenarios.
-
- If unsure, say Y.
-
-config DEBUG_INFO_DWARF4
- bool "Generate DWARF Version 4 debuginfo"
- help
- Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
-
- If you have consumers of DWARF debug info that are not ready for
- newer revisions of DWARF, you may wish to choose this or have your
- config select this.
-
-config DEBUG_INFO_DWARF5
- bool "Generate DWARF Version 5 debuginfo"
- depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
- depends on !DEBUG_INFO_BTF
- help
- Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
- 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
- draft features until 7.0), and gdb 8.0+.
-
- Changes to the structure of debug info in Version 5 allow for around
- 15-18% savings in resulting image and debug info section sizes as
- compared to DWARF Version 4. DWARF Version 5 standardizes previous
- extensions such as accelerators for symbol indexing and the format
- for fission (.dwo/.dwp) files. Users may not want to select this
- config if they rely on tooling that has not yet been updated to
- support DWARF Version 5.
-
-endchoice # "DWARF version"
-
config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
+ depends on !DEBUG_INFO_DWARF5
help
Generate deduplicated BTF type information from DWARF debug info.
Turning this on expects presence of pahole tool, which will convert
@@ -584,21 +608,6 @@ source "lib/Kconfig.kcsan"
endmenu
-config DEBUG_KERNEL
- bool "Kernel debugging"
- help
- Say Y here if you are developing drivers or trying to debug and
- identify kernel problems.
-
-config DEBUG_MISC
- bool "Miscellaneous debug code"
- default DEBUG_KERNEL
- depends on DEBUG_KERNEL
- help
- Say Y here if you need to enable miscellaneous debug code that should
- be under a more specific debug option but isn't.
-
-
menu "Memory Debugging"
source "mm/Kconfig.debug"
--
2.30.2
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